Mechanical dishwashers spray soapy hot water over dishes to clean them. The water mush be at least 140 degrees to dissolve dishwasher soap and clean greasy dishes. A higher temperature may be used to kill bacteria. In order to heat the water, a heating element is arrange around a water pump to heat the water flowing through the pump. However, it is easy to lose thermal energy from the heating element as the heating element is arranged around an outer surface of the water pump.
Hence there is a desire for a heater pump with a more efficient heating arrangement.